Small wonders can be icky as well as clicky, as this year's top images in the Nikon Small World Photomicrography Competition demonstrate. First-ever picture of the blood-brain barrier forming in a live animal? Got it. Ultra-close-ups of a desert rose and a baby garlic flower? Got 'em. Creepy pictures of bat embryos and eight-eyed spiders? Got those, too.

Ninety-nine winners were chosen out of hundreds of photographers from around the world who participated in the Small World contest, which has been presented by Nikon since 1975 to recognize excellence in photomicrography. We're featuring the top 20 images in our slideshow.

Top honors go to Jennifer Peters and Michael Taylor of St. Jude Children's Research Hospital in Nashville, Tenn., who captured what's thought to be an unprecedented picture of the blood-brain barrier in a live zebrafish embryo.

The barrier is a structure of cells that let nutrients and other necessities move between blood vessels and the central nervous system, while keeping bacteria and other baddies out of the brain's territory.

"We used fluorescent proteins to look at brain endothelial cells and watched the blood-brain barrier develop in real time," Peters and Taylor said, in a statement explaining the genesis of their winning image. "We took a three-dimensional snapshot under a confocal microscope. Then we stacked the images and compressed them into one — pseudo-coloring them in rainbow to illustrate depth."

The result is a matrix that appears to shine in the darkness like the craziest neon sculpture you've ever seen. Other winning pictures present views of a ladybug's leg, a fruit fly's gut or a bone cancer cell in similarly glowing colors.

And then there are the curiously creepy pictures: a series of three bat embryos, showing how the critters' flesh-colored wings grow longer during gestation ... an ant gripping one of its larvae in its jaws ... newborn lynx spiderlings that turn their eight eyes toward the microscope's lens.

In some cases, the photomicrographs were created in the course of a research project — but in other cases, the pictures are primarily meant to convey the wonder of small worlds. For example, photographer Charles Krebs was led to create his 17th-place image when he was stung by nettles. "After the numbness in my fingertips subsided, I carefully collected some, and took a look at the underside of a leaf," he wrote on Photomacrography.net. His 100x image shows a nettle's stinging hair, or trichome, filled with venom.

Eric Flem, communications manager for Nikon Instruments, said it was a privilege to showcase some of the world's best photomicrography. "We are proud that this competition is able to demonstrate the true power of scientific imaging and its relevance to the scientific communities as well as the general public," he said in today's news release. A total of $6,000 worth of Nikon products and equipment will go to the three top prize winnres.

Click through the top-20 slideshow, then check out the Nikon Small World website for scores of additional images of distinction. You can see the contest's top images offline as well, in the form of Nikon's full-color calendar and a touring museum exhibition. And you'll find a huge stockpile of small wonders in the slideshows listed below:

Alan Boyle is msnbc.com's science editor, and was on the judging panel for the 2011 Nikon Small World Competition. Connect with the Cosmic Log community by "liking" the log's Facebook page, following @b0yle on Twitter and adding the Cosmic Log page to your Google+ presence. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for new worlds.